Method for processing cellulose containing material to impart flame resistance

ABSTRACT

This invention relates to a new method for imparting flame resistance coupled with excellent resistance to washing to cellulose containing fibrous materials by treatment with a methylene ether bond bearing phosphorus compound.

States Yamamoto et a1.

atet 1 1 14- 1 Sept. 2, 1975 METHOD FOR PROCESSING CELLULOSE CONTAININGMATERIAL TO IMPART FLAME RESISTANCE [75] Inventors: Kosuke Yamamoto,Kamakura;

Masahiro Kono, Manazuru-machi, both of Japan [73] Assignee: MitsuiToatsu Chemicals,

Incorporated, Tokyo, Japan [22] Filed: Apr. 4, 1.974

[21] Appl. No.: 457,847

52 us. c1. 427/390;-lO6/l5 FR; 252/8.1;

260/932; 427/394; 8/116 P 51 Int. c1. c091 3/28 58 Field of Search117/136, 143 R; 252/31;

[56] References Cited UNITED STATES PATENTS 3,374,292 3/1968 Zahir117/136 X 3,381,062 4/1968 Zahir 117/143 R 3,381,063 4/1968 Zahir260/937 3,577,270 5/1971 Guth et'al 1 17/136 3,679,778 7/1972 Nachbur eta1. 117/136 X 3,700,403 l0/1972 Nachbur et al. 117/136 X PrimaryExaminer-William D. Martin Assirtant ExaminerJanyce A. Bell Attorney,Agent, or FirmLane, Aitken, Dunner & Ziems 57 1 ABSTRACT 7 Claims, 1Drawing Figure METHOD FOR PROCESSING CELLULOSE CONTAINING MATERIAL TOIMPART FLAME RESISTANCE BACKGROUND OF THE INVENTION For imparting flameresistance to cellulose containing fibrous materials, the urea phosphateprocess is conventionally employed (see, for example, Japanese PatentPublication No. 4950/1962). The cloth processed in such a manner,however, suffers from many defects, for example, p; or resistance of theflameproofing to washing, a rough finish and extremely bad feel, as wellas a large reduction in strength.

A relatively new process for flameproofing is disclosed in Japanese Pat.No. 69 l ,726. Japanese Pat. No. 691,726 discloses that certainN-methylolated phosphorus compounds bearing a methylene ether bond areeffective in processing cellulose containing fibrous materials to impartflame resistance thereto. Then N- methylolated phosphorus compoundsdisclosed therein are obtained by the condensation of3-dimethylphosphonopropionic acid methylolamide, in the presence of anorganic solvent such as toluene or benzene, followed by methylolationwith a reagent capable of generating formaldehyde. At lines 17-19 ofcolumn 21 of the specification of Japanese Pat. No. 691,726, it istaught that the non-methylolated intermediates afford no permanentflameproofing effect. The non-methylolated intermediates include thecompounds represented by formula (l) appearing at the bottom of page 38.If n of formula l0) equals 2, then formula becomes:

/PCH2CH2CNHCH2OCH2NHCCH2CHZP (I) R0 I wherein R may be the same ordifferent alkyl, alkenyl or alkoxyalkyl groups.

The N-methylolated phosphorus compounds containing a methylene etherbond, i.e., the end products used in the process as described inJapanese Pat. No. 691,726, emit a formaldehyde odor and generateformaldehyde in the course of the processing of cellulose containingfibrous materials. The noxious odor of the formaldehyde produces anundesirable working environment.

OBJECT OF THE INVENTION An object of the present invention is to impartto cellulose containing fibrous materials permanent flame resistance,that is flame resistance coupled with excel lent resistance to washing.

Another object of the present invention is to provide novelflameproofing agents which do not emit a formaledhyde odor and whichwill not generate formaldehyde in the course of flameproofingprocessing, thus improving the working environment for the flameproofingprocess.

Still another object of the present invention is to provide andadvantageous method for the preparation of flameproofing agents withwhich the above enumerated objects can be achieved.

SUMMARY OF THE INVENTION The present invention provides a method bywhich the phosphorus compounds of formula I, having a 5 methylene etherbond but no N-methylol groups, can

be utilized to impart permanent flame resistance to cellulosic fibers;that is, flame resistance coupled with excellent resistance to washing.As previously noted, the compounds of formula I have not previously beenrecognized to have such a utility.

In accordance with the method of the invention, it is possible togreatly improve the working environment for the flameproofing processingof cellulose containing fibrous materials.

The present invention also provides an easy method for the preparationof phosphorus compounds having a methylene ether bond out no N-methylolgroup, i.e. the compounds represented by formula I.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows an infrared adsorptionspectra chart for one of the compounds of formula I, i.e. N,N'-oxymethylenebis (dimethylphosphonopropion) amide.

DETAILED DESCRIPTION OF THE INVENTION As previously noted, the presentinvention provides a method for the utilization of the phosphoruscompounds having a methylene ether bond but no N- methylol groupsrepresented by formula I(hereinafter referred to as phosphorus compoundsI) as agents for flameproofing cellulose containing fibrous materials.

On the other hand, phosphorus compounds similar to those of formula Iand represented by the following general formula II 35 R 0 ORPCH2CH2CNHCH2HNCCH2CH2P (II) R 0 OR 2 o o o o 4 (I) (II) +CI-I OHowever, when cellulose containing fibrous materials are processed forflameproofing with the phosphorus compounds I in accordance with themethod of the present invention, the conversion of methylene ether bondinto the methylene bond does not occur under general processingconditions. Although it is not completely clear why the methylene etherbond in the phosphorus compounds of formula I does not change into amethylene bond under general processing conditions,

it is theorized that, since the bond to the cellulose is a phosphoruscompounds of formula I used in the monomolecular attachment, as in acidhydrolysis in almethod of the present invention is optional; however,cohol, the methylene ether bond splits off and simultathe followingthree processes are preferred: neously reacts with the hydroxy group inthe cellulose The first process comprises condensation with water fiberthereby attaching to the cellulose fiber in the form 5 removal, in thepresence of an acid catalyst such as of phosphonopropionamidomethylether. p-toluenesulfonic acid, of the monomethylol derivative Asdescribed in the foregoing, the methylene ether of, for example,d-dimethylphosphonopropionamide, bond in the phosphorus compounds I usedin the as described in the published specification of Japanese method ofthe present invention is a potential func- Patent No. 646,127, Thisreaction may be represented tional group which splits off underprocessing condiby the following equation 2:

-H O PCH CH CNHCH OH 9 I (2 R26 O O tions and reacts with the cellulosefiber. Accordingly, With this first process, however, it is difficult toproother functional groups reactive with cellulose fibers, 2O ducephosphorus compounds I of relatively high purity such as the N-methylolradicals of the compounds used n h r f orma de yd tends to remain n h inthe process of the above described Japanese Pat. No. produ t. 691,726,are unnecessary. A second and more preferred process comprises con- Thespecification of japanese Pat. No. 691,726 densation ofN,N'-oxydimethylenebisacrylamide and a teaches that the phosphoruscompounds I exhibit no phosphorous acid diester, either in the presenceof a permanent flameproofing effect. However, phosphorus solvent such asdioxane or in the absence of a solvent, compounds I show an excellentpermanent flameproofand in the presence of a basic catalyst such assodium ing effect as demonstrated by the following examples: methoxide,as depicted in the following equation 3:

R O (CH =CHCNHCH o POH---' (I) (3) The discrepancy with regard toobservations as to the However, the process for the preparation of N,N'-

permanent flameproofing effect of compounds Iindioxydimethylenebisacrylamide used as the starting ma cates, as willbe shown in the examples to follow, that terial in this second method isrelatively complicated the phosphorus compounds I must be produced withand moreover the impurities contained in the N,N'- carefully controlledprocess conditions. oxydimethylenebisacrylamide adversely affect thecat- In the steps for manufacturing the phosphorus com- 40 alyst used inthe reaction depicted above by equation pounds I and, in particular, inthe step in hich the 3, and requires purification by methods such asrecrysmethylene ether bond is introduced it is necessary to tallization.As a consequence, this method represents a carefully adjust reactionconditions. When the reaction relatively expensive route for theproduction of the conditions are not optimized, for example when the pHcompounds of formula I. in the reaction system is too low, when thereaction The third process, which is the most preferred of the.temperature is too high or when the water content in three, comprisescondensing a phosphonopropionathe reaction system is too high, themethylene ether mide, in the presence of an acid catalyst, with aformalbond changes into a methylene bond as depicted in dehyde source todirectly produce the phosphorus equation 1. Accordingly, it may betheorized that the compounds I, as depicted in the following equation 4:

PCH CH CH CNH CH O 5:21 (I) H O (4) R 0 u n O 0 process described in thepublished specification in Jap- It is well known in the art that when anacid amide anese Pat. No. 691,726 must not have been properly iscondensed with formaldehyde under acid conditions, controlled and eitherdid not actually produce the comthe corresponding methylenebisamidecompound pounds represented by formula I or produced a mixture forms. Aphosphonopropionamide, when condensed containing only small amounts ofthose compounds. with formaldehyde, forms a methylene compound as Theparticular process for the preparation of the depicted by the followingequation 5:

PCH CH CNH CH O) (II) H The formation of a methylene compound inaccordance with the reaction depicted in equation 5, however. takesplace only when the pH of the reaction system is strongly acidic, thatis, not higher than 0.5. When the pH of the reaction system is in therange of form 0.5 to 5 reaction (5) does not occur but, rather, aphosphorus compound of formula 1 forms according to the reaction asdepicted by equation 4. Thus, when the condensation reaction of aphosphonopropionamide with formaldehyde is conducted in an acidicmedium, it is possible to restrict the reaction to the production ofmethylene ether bond bearing phosphorus compounds I, only, withoutforming by-product methylene compounds, only if the pH in the reactionsystem is closely controlled.

The optimum pH in the reaction system for the pro duction of thephosphorus compounds I according to the process represented by equation4 will vary to some degree with the reaction temperature, although itshould generally be within the range of from 0.5 to 5, and preferablywithin the range of 2 to 4. The use of a pH outside the range of 0.5 to5 is undesirable because when the pH of the reaction system is less than0.5 methylene compounds form. On the other hand, when the pH of thereaction system is above about 5, a higher temperature and a longerreaction time are required and side reactions resulting in the formationof impurites are increased. Such side reactions include, for example,the Cannizzaro reaction of formaldehyde, hydrolytic reactions of amidegroups and hydrolytic reactions of the phosphoric acid esters.

Suitable acidic agents for the adjustment of the pH of the reactionsystem to 0.5 to 50 to include, for example, inorganic acids such ashydrochloric acid, sulfuric acid and phosphoric acid, organic acids suchas p-toluenesulfonic acid, and strongly acidic ion exchange resins.

The reaction temperature in the process of equation 4 should be set inaccordance with the pH of the reaction system, although it shouldgenerally be within the range of from 30 to 140C and preferably withinthe range of 50 to 90C.

Suitable formaldehyde sources which may be used in this process includeany compound capable of releasing formaldehyde in an acidic medium, forexample, polyoxymethylenedialkylethers, trioxane, tetraoxane, para-.

formaldehyde or an aqueous formaldehyde solution. From the standpoint ofthe ease of the reaction procedure, paraformaldehyde in concentrationsnot higher than 80 percent by weight and aqueous formaldehyde solutionsare preferred formaldehyde sources.

The reaction depicted by equation 4 is a reversible equilibriumreaction. It is therefore desirable, for achieving complete conversionof the starting materials to the phosphorus compounds of formula I, toremove from the reaction system by-product Water as Well as that waterintroduced with the formaldehyde source. For removal of water from thereaction system, distillation under normal pressure suffices, although,from the standpoint of depression of side reactions and inhibition ofvaporization of the formaldehyde source, it is more advantageous toemploy a method wherein the water is distilled off under reducedpressure or wherein the water is azeotropically removed. Solventssuitable for use in azeotropic distillation include those solventswhich, after cooling, seprate from the aqueous phase,

' for example benzene, toluene, cyclohexane and carbon tetrachloride.

The methylene ether bond in the phosphorus compounds I obtained by theabove enumerated varied processes can easily be quantitativelydetermined by, for example, infrared absorption spectroscopy, orchemical analysis wherein the formaldehyde content after decompositionwith a dilute aqueous acid solution is quantitatively determined.

In the phosphorus compounds I used in the method according to thepresent invention, R to R are the same or different alkyl, alkenyl oralkoxyalkyl groups and each have not more than 10 carbon atoms, andpreferably not more than 4 carbon atoms. Of these groups, the alkyl andhalogen alkyl groups are preferred and R R R and R are preferablymethyl, isopropyl or chloroethyl groups.

The reaction catalysts used for treating cellulose containing materialswith the phosphorus compounds of formula I are conventional. Thosecatalysts known to be useful in curing amino resins, for example,ammonium chloride, orthophosphoric acid, magnesium chloride, zincnitrate or Zinc borofluoride, can be used.

The concentration in the processing bath of the particular phosphoruscompound of formula I used may vary with the desired degree of flameresistance to be imparted. A suitable concentration range is from 5 topercent by weight, and preferably from 20 to 50 percent by weight.

In impregnating a cellulosic material with the above describedprocessingsolution, a variety of conventional methods may be applied,such as pressing between rolls, spraying or centrifugation. In addition,the manner of drying may be by any means and drying at any temperaturebetween room temperature and 200C suffices. With regard to curingconditions, satisfactory results are obtainable by curing attemperatures, of the order of from 120 to 200C for periods of time offrom 30 seconds to 10 minutes.

In conjunction with the method of the present invention, amino resinsmay be applied without difficulty. Suitable amino resins includereaction products of a variety of low molecular amino compounds usuallyused as the starting materials for the manufacture of amino resins, forexample, urea, melamine, thiourea, ethylene urea, guanidine or urone,with formaldehyde, as well as the alkoxylated derivatives thereof.

When such amino resins are applied in conjunction with the presentinvention, however, the working environment will be adversely affecteddue to the generation of formaldehyde. On the other hand, when thephosphorus compounds I are used alone in accordance with the method ofthe invention, formaldehyde is not generated and therefore the workingenvironment is not adversely affected. For this reasons, the use of thephosphorus compounds I without the presence of amino resins ispreferred.

EXAMPLE 1 A solution of 184 g (1 mole) N,N- oxymethylenebisacrylamideand 242 g (2.2 moles) dimethyl phosphite in 300 cc dioxane is heated to40C and a methanolic sodium methoxide solution (8 g sodium, g methanol)as catalyst added in portions with stirring. After the addition ofapproximately twothirds volume of the sodium methoxide solution, anexothermic reaction takes place and the reaction temperature rises.Subsequently, the catalyst is added in portions in such a manner as tomaintain the reaction temperature at 80C. When the addition of thecatalyst is complete, stirring is continued at the same temperature forabout one hour to complete the reaction. The reaction mixture isdistilled under reduced pressure to remove dioxane and excessivedimethyl phosphite. thus giving 407 g N,N-oxymethylenebis(dimethylphosphonopropion) amide (general formula (1), R R CH as a clearviscous liquid.

No free formaldehyde was found in this product but formaldehyde in theform of methylol or methylene ether was 0.08 or 14.71 percent (asformaldehyde), respectively. These values indicate the product to be of99.1 percent purity.

The infrared spectra for this product is shown in FIG. 1.

A cotton twill was then treated in a processing bath containing a 30percent aqueous solution of N,N- oxymethylenebis(dimethylphosphonopropion) amide and 0.4 percent ammonium chloride,dried at 90C and cured at 150C for 4 minutes. The processed cloth wasincombustible in the flame resistance test conducted after washing.

EXAMPLE 2 A flame resistance test was conducted with a cotton twillprocessed with various N,N-omymethylenebis (phosphonopropion) amides.The compositions of the respective processing baths as well as the testresults before and after washing are shown in Table l.

The processing procedure was as follows: The cloth was, afterimpregnation, picked up (80 percent by weight pick up), dried at 90C for4 minutes and cured at 150C for 4 minutes.

The cured cloth was subjected to minutes soaping at 40C using a 0.2percent by weight detergent (manufactured by Kao Sekken Co., Ltd.; TradeName ZABU) aqueous solution and then rinsed for 5 minutes with water.This procedure was repeated five times. The finally dried cloth was usedas the test cloth The flame resistance test was conducted in accordancewith Japanese Industrial Standards (JIS) -L- 1091 A- 1. This test methodis the 45 microburner method. The test cloth is spread over a 25 X 15 cmframe and set in a combustion test chamber at an angle of 45. Themicroburner is ignited, the cloth heated for one minute and the flameduration time (the length of time from the end of heating to a pointwhere flaming of the test cloth ends) is determined. The microburner isadjusted beforehand in a manner such that the length of the flame is 4.5cm and the tip thereof is in contact with the test cloth. Subsequentlythe test cloth is separated from the flame and the carbonized length andarea are determined. Picked up means squeezed, rung, etc. 80 percent byweight pick up means that 80 percent of the water was removed.

EXAMPLE 3 41 g of an aqueous solution containing 80 percent by weightparaformaldehyde was suspended in 181 g 1.0 mole)dimethylphosphonopropionamide and the reaction system adjusted to a pHof 3.0 by the addition of p-toluenesulfonic acid and heated, withstirring, to 80C. In 2 hours the suspension became a clear solution. Thesolution was stirred for an additional three hours to complete thereaction. The reaction mixture was distilled under reduced pressure toremove water and excessive formaldehyde. The product was N,N-oxydimethylenebis( dimethylphosphonopropion) amide of 97.4 percentpurity with a yield 202 g.

A flameproofing bath was prepared from a 35 percent by weight aqueoussolution of the above product to which solution 3 percent phosphoricacid had been added, and the processing conducted as in Example 2,whereupon no odor of formaldehyde was detected.

The processed cloth was subjected to 5 minutes soaping with an aqueoussolution containing 0.3 percent sodium carbonate and 0.3 percent ZABU.Subsequently, the procedure of 15 minutes soaping at C in a 0.3 percentaqueous ZABU solution and 3 minutes rinsing at 50C was repeated fivetimes and the cloth finally dried at 100C for 3 minutes.

The flame resistance test results with this test cloth were as follows:carbonized area 20 cm; carbonized length 6.0 cm; and flame duration orlasting time 0 secfor after washing. d

Table 1 R,,R;. Processing Bath (71 by weight) Before Washing AfterWashing Carbo- Carbo- Flame Carbo- Carbo- Flame nized nized lastingnized nized lasting Active T- MgCl L length area time length area time(CH agent 36* NH,C1 H PO, GH O (cm) (cm'-') (sec) (cm) (cm'-) (sec) 25 s0.5 6.8 20 0 7.0 22 0 II l5 8 (1.5 6.6 23 U 6.6 25 O (C H 35 8 3 6.8 220 6,7 27 0 (ClCH CH 25 8 3 6.7 21 0 6.9 24 0 (C1 C ,H 25 s 3 6.8 22 0 as23 0 (B,.CH CH 30 8 3 618 22 O 6.8 26 ca-I 25 x 3 6.9 23 0 7.4 32 00,11,00,11, 30 s 2 7.0 20 0 7.7 36 0 (C,,H 25 s 2 6.6 23 0 6.9 29 0CH,,, C. .H,, 25 0 2 6.6 22 0 6.8 31 0 (C H 30 8 0.5 6.7 23 0 7.0 28 O(i-C;,H;) 25 x 0.5 as 22 0 7.3 32 0 Trade name --Ulamine T-3l1" for /raqueous melhoxymethylnlmelamine solution manufacture by Mitsui ToatsuChemical Co., Ltd.

We claim: 2. The method of claim 1 wherein R R R and R 1. A method forflameproofing cellulose containing are alkyl or halogenalkyl groupshaving not more than material comprising: 4 carbon atoms.

providing a solution containing a phosphorus com- 3. The method of claim1 wherein the phosphorus pound represented by the following general for-5 compound is prepared by condensing a phosphonopromula: pionamide withparaformaldehyde in the presence of an acid catalyst. R 0R 4. The methodof claim 2 wherein R R R and R are a met y groups. /PCH CH CNHCH OCHNHCCH CH P l0 5. The method of claim 2 wherein R R R and R are all isor0 1 rou s. 2 g A B4 6. The r t let dif claim 2 wherein R R R and R areall chloroethyl groups.

7. The method of claim 1 wherein the material is apwherein R to R arethe same or different alkyl, alkeplied the form of an aqueous Solutioncontaining n l, h l lk l or lk lk l groups; 5-80 percent by weight ofsaid compounds to wet the applying said oluti t th ll l i containingmaterial and wherein the wetted material is dried and material; andcured at a temperature within the range of 120 to drying the cellulosiccontaining material.

1. A METHOD FOR FLAMEPROOFING CELLULOSE CONTAINING MATERIAL COMPRISING:PROVIDING A SOLUTION CONTAINING A PHOSPHORUS COMPOUND REPRESENTED BY THEFOLLOWING GENERAL FORMULA:R1-O-P(=O)(-O-R2)-CH2-CH2-CO-NH-CH2-O-CH2-NH-COCH2-CH2-P(=O)(-O-R3)-O-R4WHEREIN R1 TO R4 ARE THE SAME OR DIFFERENT ALKYL, ALEKNYL, HALOGENALKYLOR ALKOXYALKYL GROUPS, APPLYING SAID SOLUTION TO THE CELLULOSICCONTAINING MATERIAL, AND DRYING THE CELLULOSIC CONTAINING MATERIAL. 2.The method of claim 1 wherein R1, R2, R3 and R4 are alkyl orhalogenalkyl groups having not more than 4 carbon atoms.
 3. The methodof claim 1 wherein the phosphorus compound is prepared by condensing aphosphonopropionamide with paraformaldehyde in the presence of an acidcatalyst.
 4. The method of claim 2 wherein R1, R2, R3 and R4 are allmethyl groups.
 5. The method of claim 2 wherein R1, R2, R3 and R4 areall isopropyl groups.
 6. The method of claim 2 wherein R1, R2, R3 and R4are all chloroethyl groups.
 7. The method of claim 1 wherein thematerial is applied in the form of an aqueous solution containing 5-80percent by weight of said compounds to wet the material and wherein thewetted material is dried and cured at a temperature within the range of120* to 200*C.